The present invention relates to an image recording apparatus for recording an image in an image support such as a microfilm with retrieval marks.
In a conventional retrieval device incorporated in a film reader, its film has retrieval marks respectively formed on peripheral portions around the frames. These marks are optically detected and counted to automatically retrieve a desired frame in the film.
In the retrieval device, the mark on the film is irradiated with light from a lamp, and a mark detector detects a change in light shielded by the mark upon movement of the film. Output pulses from the mark detector are counted by a counter. A count of the counter is compared by a comparator with a desired frame number input at a keyboard or the like. If a coincidence between the count and the input frame number occurs, the comparator supplies a stop signal to a drive control circuit. The drive control circuit then causes a drive system to stop feeding the film. Therefore, a desired frame is stopped at a predetermined position so that the image thereof is projected on the screen.
Most images recorded in the microfilms are negative images. In order to obtain positive images from these negative images, reversal development is employed. In reversal development, a developing toner having the same polarity as that of an electrostatic latent image is applied to a photosensitive drum with the latent image when copying is performed according to an electrophotographic copying method. More specifically, the photosensitive drum is uniformly charged and the negative image of the microfilm is exposed thereon to leave a charge on a nonexposed portion of the photosensitive drum. The toner charged at the same polarity as that of the charged nonexposed portion is attracted to the exposed portion of the photosensitive drum, thereby achieving reversal development.
In a conventional microfilm having negative images, the negative images are respectively recorded within frames 30 of a microfilm F, as shown in FIG. 3. The peripheral portions of the respective frames are transparent, and opaque retrieval marks 31 are recorded in the peripheral portions of the frames 30, respectively. In a conventional reader printer using a microfilm, an area larger than the size of each frame 30 of the microfilm is projected on a photosensitive body.
In a conventional technique of this type, the negative image in the microfilm is projected onto a photosensitive body and reversal development is performed to apply a toner to a region corresponding to the outside of the image of the frame 30 on the photosensitive body. A so-called black frame is recorded around the image on the photosensitive body so that the corresponding retrieval mark is also recorded, resulting in poor appearance. The value of the copy as a commercial product is reduced. In addition, when electrophotographic copying is performed, toner consumption is increased. In order to solve these problems, a mask having an opening corresponding to the size of one frame of the microfilm is brought into contact with the surface portion of the corresponding frame of the microfilm. However, if frames have different sizes, the mask must be replaced with the corresponding ones, resulting in inconvenience. In addition, since the retrieval mark is not projected onto the screen, it is impossible to retrieve a desired frame by utilizing the retrieval mark.
A conventional reader printer having a microfilm as an original image includes an automatic image density adjustor to obtain a printout with an optimal image density. In the automatic image density adjustor, an original image is irradiated with light having a predetermined amount of light to scan the original image with a light-receiving element. Amounts of light of the background and image portions of the original image are detected according to the outputs from the light-receiving element. The optimal value of the exposure level or the development bias voltage level as an image formation condition is obtained according to the detection information.
In the conventional system of this type, however, since a portion around the frame 30 in the microfilm F is transparent, the amount of light from the transparent portion around the frame is greater than that through the frame and serves as an image density determination factor for detecting an image density. As a result, an optimal image density of the necessary frame image area cannot be obtained with accuracy.